This invention relates to vehicle wheel alignment systems, and in particular to method and apparatus for adjusting toe.
Proper alignment of wheels in a vehicle is important for proper handling of the vehicle and proper tire wear. The alignment of a vehicle's wheels is performed primarily by adjusting camber, caster, steering axis inclination (SAI) and toe. Of paramount importance to the driver of the vehicle is that the vehicle drive straight down the mad when the steering wheel is held in its straight or rest position. This condition is a function of toe of the vehicle, and in particular is affected by the relative toe of one wheel on the steering axle with respect to the other.
Heretofore, the method of adjusting toe on a vehicle was relatively complicated. The toe of each wheel on the steering axle is conventionally compared to a toe specification value for that wheel and vehicle, and the total toe is also compared with a total toe specification value for the vehicle. This procedure frequently required repeated attempts to get the individual toe values and the total toe to fall within specification. The prior art method also required locking the steering wheel in the straight ahead position, since any change in the steering wheel position would adversely affect the measurement of the individual toe values.
Even with all this work on the part of the technician/user, correcting the toe of the wheels to specification did not always result in the vehicle driving straight ahead when the steering wheel was held in the straight ahead position. The tolerances on these specifications are such that adjusting each wheel to within the tolerance of the specification can result in substantial unbalanced side forces being applied by the wheels.